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276 AMD Geode™ LX Processors Data Book
Graphics Processor Register Definitions
33234H
6.4.2.25 LUT Index (GP_LUT_INDEX)
This register is used to initialize the LUT_INDEX pointer that is used for subsequent LUT operations. All LUT accesses are
DWORD accesses so only the 9 LSBs of the pointer are used to index into the 2 KB LUT. Addresses 000h-0FFh are used
for 8-bit indexed LUT data. Addresses 000h-00Fh are used for 4-bit indexed LUT data. Addresses 100h-13Fh are used for
storing color patterns. All addresses are used for storing incoming data (unless the PL bit is set in the
GP_CH3_MODE_STR register, GP Memory Offset 64h[20]), but none of the remaining addresses have any significance to
software.
6.4.2.26 LUT Data (GP_LUT_DATA)
This register is used to store data into the LUT for indexed color translations and color patterns. The 32 bits written to this
register are stored in the LUT at the location specified in the GP_LUT_INDEX register (GP Memory Offset 70h). A read of
this register returns the contents of the LUT at the location specified by the GP_LUT_INDEX register. Either a read or write
of this register will cause the GP_LUT_INDEX register to increment, so the LUT can be loaded through successive writes to
the GP_LUT_DATA register.
GP Memory Offset 70h
Typ e R /W
Reset Value 00000000h
GP_CH3_HSRC Register Map
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RSVD LUT_INDEX
GP_CH3_HSRC Bit Descriptions
Bit Name Description
31:9 RSVD Reserved.
8:0 LUT_INDEX LUT Index. Used to initialize the LUT_INDEX pointer that is used for subsequent LUT
operations. The LUT_INDEX automatically increments on a write to the GP_LUT_DATA
register (GP Memory Offset 74h). When performing a read, bit 31 must be set to cause
the hardware to perform the read and update the GP_LUT_DATA register. If this bit is not
set, then a write is assumed and the read will not be performed.
GP Memory Offset 74h
Typ e R /W
Reset Value xxxxxxxxh
GP_CH3_HSRC Register Map
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
LUT_DATA
GP_CH3_HSRC Bit Descriptions
Bit Name Description
31:0 LUT_DATA LUT_DATA. Used to store data into the LUT for indexed color translations and color pat-
terns.